A conventional fan rotor for compressing air comprises a disc having a plurality of radially extending blades mounted thereon. The fan blades are mounted on the disc by inserting the radially inner end of the blades in correspondingly shaped retention grooves in the radially outer face of the disc. The fan blades do not have platforms so the inner wall of an annulus for the compressed air is formed by fastening separate wall members to the radially outer face of the disc. The separate wall members bridge the space between pairs of adjacent blades to define the inner annulus wall.
Each separate wall member has resilient strips bonded to the edges adjacent the fan blades. The resilient strips protrude so that they abut the adjacent fan blades. The resilient strips thus seal between the wall members and the fan blade to prevent air leaking past the inner wall of the flow annulus.
A drawback of such an arrangement is that the resilient strips are a close fit with the adjacent blades which leads to difficulties in assembly.